Chair with self-adjusting back



July 22, 1952 H. E. SMITH ETAL CHAIR WITH SELF-ADJUSTING BACK Filed Oct. 20, 1948 Patented July 22, 1952 '.I-Zhis. .inventionrelates 4to a .chair `of, the tsocalled .self-'adjusting type in which the inclinationfof vthe chair-back may-be changed-,merelyfby the occupantsapplication or release :of pressure against the back. Such cha-irs,v as 'heretoforemade, commonly embody apvotally mounted b'ack,spring means for yurgi-ng1th'e back'for-f wardl-y, and frictionalbrake meansfor lopposing movement of. theback in/eitherdirection.

,Itis the. object-of your invention to improve :the construction vand operation 4of self-adjusting chairs. .More specifically, it is four object Vto pro-1 mechanism which -can be readily 'adjusted rtomeet thev desireslof the-occupant-of -the chair.

.Incarryng out ,ourinvention, we mount' the chair-.back for ,pivotal .adjustment-about :an :axis located approximately at the lintersectionof 4the load-supporting surfaces of the seat `and back. Thelback is yconnected asthrough 'a link with `a reciprocable wedge-shapedbrake 'member lagainst the -obliquely disposed -faces `of whichfagpai-r 'of' brake-:shoes lbear. In the preferred form vof construction,.one-of such shoes is stationary with :respect -to `the base frarneof lthe chair, 4while the other :shoe Yis -mounted for A'free :swinging movement-at an intermediate :point 'ofza lever pivoted to the base frframe. .A spring,'which;is .desirahly adjustable, .acts V`against such lever to :forceithe associated Vbrake-shoe against the v.adjacent .rside of 'the-brake imember. The :arrangement of :the parts is such'ithat .the resultant lof the: fforces exerted :by the 'brake shoeslon rthe cbliquly dis-'- posed sides .of `the brake .member tends to Amove the back forwardly toward an upright position. Desirably, the lever nis Vso shaped and disposed thatsas it swings.changes in the lever arm of the force exerted on it by the lever-mounted brakeshoe will at least partially offsetv changes in the force exerted on -the lever by Vthe spring.

The accompanying drawing illustrates our :invention: Fig. .1 is a vertical sectionon the line I--I of Fig. 2 showing the back-controlling mechanism in side elevation; rFig. 2 is a `fragmental vertical transverse section-on the linel22 of '.Figflshowing the right side-'ofthe chairyand Fig. 3 is a similar section but on the line 3-3 of Fig. 1 and showing the left side of the chair.

'I'he chair shown in the drawing comprises a solaires'. (01.155916-1) pair of `generally. similar side `frames .Iprigidly interconnectedby-:front and rear stretchers I I. andv l2. -The side .frames `Illhand the Astretchers. II andi-:2 constitutea-,base structure supporting a `springunit-Lion-which aseat cushion L4 rests. The .chair also` vembodies-a back having `a back frame` -I-5the frontfof which is covered .by cushioned aupholstery i6. To-each side of `the back` frame l5 and near ythe ylower -end thereof there is. secured amounting bracket lI'I- pvotally `connected to theadj-acent side frame I' 'asby means of a shaft I.-8 mounted in such -side fra'me. The two Asha-its If8- on vthe vtwo side fra-mes I0 are located in' alignment with eachother approximately at the intersection or the load-.supportingsurfaces. of the sea-,t `and bar/lecushionsv |14 and lli' when the chair isoccupied.

.At each fsidje :of Ithe ychaifiwand Within .the :side frame Ill, we dispose mechanism foi-@controlling theiposition of ,the chain-'back' about the :axis .of theqshafts 118. These `.mechanisms .are the same, andhencel only oneof'rthem. will' be described. Referringto fFig. l, it vvillibe obvious that each Iof the; brackets Isl ais connectedlatv va :point displaced from ithe sha-ft I8 with-:oneendof a link i2-@which extends forwardly and 'downwardly zfor pivotal connection with a brake member 2|. Suchbrake memberis-gnera'lly wedge-'shaped' and h-asa pair ofV plane' brakesurf aces .disposed at 'an .acute angle to feach other. One :of Vsuch surfaces isy disposed horizontally 'to rest Von afbrake shoe Y2-2 mounted in a horizontal position o-n llthe side frame I'0. Thevother surface, which is inclined lforwardly and downwardly, vcol-operates with a brake shoe 23- pvotally mounted, -as-on a pin or yrvetl 24, at an'in-t-ermedi'ate point of 1a lever 25.` Both'of the brake 4shoes 1-22 and -23 are faced with friction material such as the 'brake-lining material commonly used in the brak'esof automotive vehicles.`

The -leverf2h5has its lower end pvotally connected to the side `frame 'IB yin advance ofthe brakes-11015122 and extends-generally rearwardly andupwardly, being-connected at its Iupper end to the lfronti-:nd of a tensionspring l2 'I the rear lend of whichfis connected withthe side lframe I0,

desirably'through 'an adjusting device whereby the Lforceexertf-:d on 'the lever -2.5 by the spring may bevaried. As'shown, such adjusting device.

takes the 'form-,cfa lcablelil which is Aconnected .to thegrear end of the spring 2"I,passes over a pulley-29 rotatablymountedin the sideframelll, and extends downwardly from such `pulley to a transversely extending horizontal Vshaft (id-.t0 whichjthe lower end of vthe cable 28 issecured. The shaft '39 extends Ycomplately across thechaii, and Athe 'cables 28 o'f both back-controlling mechanisms are .secured to .,it. Inside one-ofthe side frames I0, =a worm wheel 32 is secured to the shaft 30 in position to mesh with a worm 33 rotatably supported in a bracket 34 secured to vfar describedl that the spring 21by urging the upper end of the lever rearwardly, will cause both brake shoes 22 and 23 to bear against the Y respectively adjacent, obliquely disposed sides of the brake member 2|. If the contact of the brake shoes with the sides of the brake member were frictionless or substantially so, the resultant of the pressures exerted by the brake shoes on the brake member would be directed upwardly and rearwardly and, transmitted to the chair-back through the link 20, would urge the back forwardly. However, contact of the brake shoes with the brake member is not frictionless; and to the extent that it is not frictionless, the effect of brake-shoe pressure on the brake member in urging the chair forwardly is reduced. By properlyco-ordinating the angle between the brake surfaces of the brake member `2| withthe coefficient of friction between the brake shoes and those surfaces, the effectiveness of the spring V2'l in urging the chair-back forwardly can be reduced to any extent desired or eliminated entirely. Desirably, the angle between the surface of thebrake member 2| is such that the spring 21 has little if any effect in urging the chair-'back to swing forwardly about the shafts I8. When this is the case, we employ means such as a spring 31 acting between'the brake member 2| Vand a fixed abutment on the side frame lll to urge the brake member 2| rearwardly and hence to bias thechair-back for Vforward swinging. v

The chair-back is shown in full lines in Fig. 1 in the position it assumes when the chair is not occupied or when the occupant of the vchair is not leaning against it Vwith any substantial effort. VIn this condition; the chair-back is inclined slightly to the rear, and the force of gravity acting on it would normally tend to cause it to swing rearwardly. However, rearward swing:-l ing ofthe back would entail forward movementv of the brake member 2| and extension of thetwo springs 21 and 31, as well as the overcoming'of the friction between the-brake rmember 2|A and the two brakev shoes 22 and'23. As a result of the eii'ect of friction and of the forces exerted by the two springs, the chair-back will remain' in the position indicated until a rearward presf sure greater than a predetermined value is exerted'against it. If an occupant of the chair desires to increase the rearward inclination of the back,'he merely increases the pressure against it to an extent suicient to overcome the, effects of the two springs 21 and 31 and of the friction exerted-onthe brake member 2| by the two brake shoes 22 and 23. If desired, the occupant may apply suicient pressure to the chair-back to swing it into a substantially horizontal position, such as is indicatedV in dotted lines in Fig. 1. Having adjusted the chair-back to the desired degree of inclination, the occupant may then reduce considerably the pressure exerted against it without permitting forward swinging of the chair-back, for the friction between the brake member and brake shoes will oppose such forward swinging. If the parts are .properly proportionedrelease,of allrearward and downward pressure from the chair-back will cause it to move slowly position."

Itwill be apparent Vfrom Fig. 1 that rthe fricy toward its normal, nearly upright voffering a substantial resistance to lowering of the back. As a result, the supplementary spring 31 can be much lighter than it would otherwise have to be, It will also be noted that no movement of the back can occur without movement of the brake member 2| relative to the shoes 2| and 22,y and that the brake mechanism therefore functions to hold the back in fixed position until the force applied to it becomes great enough to overcome the effect of friction between the brake member and shoes.

We claim as our invention:

1. In a self-adjusting chair, a seat, aback pivotally mounted on a horizontal axis for swinging movement relative to thes'eat, a brake member having brakesurfaces disposed at an acute angle to each other, brake shoes respectively engaging said surfaces, yielding means acting'to urge said shoes toward each other, said brake vmember being movable in the plane of said acute angle and toward the apex thereof to force the brake shoes apart and away from such apex to permit the brake shoes to approach each other under the influence of said yielding means, and mechanism interconnecting said back and brake member to cause said brake member to force said shoes apart when the back is swung rearwardly from a vertical position. y. Y 1

2. The invention set forth in claim 1- with the addition of a second yielding meansv urging said back forwardly toward a vertical position. y 'i i 3. The inventionset forth in claim 1 with the addition that said yielding means isadjustable.

4. In a self-adjusting chair,y a base, a seaton` the base, a back vpivo'tally supported from said base on a vhorizontal axis for swinging movementv engaging said brake shoe and the other inclined' forwardly and downwardly, a lever fulcrumed on saidbase in advanceofl said brake shoe and extending upwardly, a lsecond brake shoe pivotally' mounted on said lever'and engaging the inclinedV Y face of the brake'member, 'and a springY forurgling the upper end of said lever rearwardly.

HOMER E. SMITH. WM. B. BEUI-ILER i REFERENCES CITED The following references areof record in *the le of this patent: v Y UNITED STATES PATENTS Number Name Date 2,252,097v i Rockenfleld` Aug. 12, 1941 2,273,428

Bankl Feb. 17, 1942 K 

